Police say early Monday morning, three men were seen on school surveillance videos breaking in and stealing 58 Mac laptop computers and two desktop computers from West Philadelphia High School.

Lt. John Walker with the Philadelphia Police Department said, “Unfortunately, the persons inside the school around 2 a.m. are wearing masks and gloves. So we can’t really make an identity as to who they are.”

West Philadelphia High School is the latest target in a string of costly computer thefts in the district.

Authorities say since 2009, nine schools have been hit and 384 computers were reported stolen.

Officials say it costs the district $1,300 to replace one computer.

That means these thefts could cost the district $499,200 to replace the stolen computers. Authorities say they normally depend on grant money to pay for such purchases.

District Spokesman Fernando Gallard said, “We have had occasions in which we’ve gotten the equipment back.”

That happened last October, following the arrest of Kathleen Kremis, then fifth grade teacher, and her ex-husband, Thomas Perry. Police say they stole from Ethan Allen Elementary School and sold the computers to a pawn shop.

Turns out, all school computers are tagged with an “ID sticker.”

Gallard explained, “When you do take it off, there’s a chemical tattoo that’s attached to the equipment. So even if you try to take that off, you can tell the equipment is the property of the School District of Philadelphia.”

Gallard says the district is conducting a full review of its security system at the school as a result of the incident.

Officials say West Philadelphia High School is secured with an alarm system. Officials are now trying to determine why the alarms were not triggered.

Police are also asking anyone who is offered new or almost new Mac laptops on the streets for far less than what it’s worth to do the right thing and call the police.